The present invention relates to noise cancellation in disc drives, and more particularly to an active noise cancellation device mounted to a disc drive case operated to cancel or reduce noise in the disc drive.
High performance disc drives are being developed to accommodate increasingly higher frequencies of data recording, resulting in higher rotational speeds (e.g. 10,000 revolutions per minute) of the disc and the spindle. High spindle speed introduces or magnifies problems in the environmental dynamics of the disc drive, creating acoustic noise-producing vibrations. Moreover, the higher air velocity in the disc drive creates oscillations, cavitations and vortexes around components of the drive, contributing to the noise generated in the drive. In addition, noise is generated by the disc drive actuation system during seek operations. All of this noise is undesirable due to its negative effect on both the performance accuracy and user appreciation of the disc drive.
Passive damping techniques are commonly used to reduce high frequency noise in disc drives. Examples of passive damping include a resilient frame or shock mounts, noise-absorbing insulation, and the like. However, the noise-producing vibrations caused by increased spindle rotation speed and actuator seek operations are low frequency signals, often having a frequency as low as audible noise, and the passive damping techniques are not altogether effective in damping low frequency acoustic noise signals. Accordingly, additional noise reduction and cancellation techniques are required to effectively contain or cancel these low frequency noise components.